The present invention relates to a device, assembly and method for the passive reduction of sound vibrations in a liquid, in particular water, resulting from a sound source arranged below the liquid level.
During underwater operations, relatively high noise levels may be generated which can be harmful to animals or humans situated nearby. If, for example, pile-driving has to be carried out under water, in which case a pile element, such as for example a pile, is driven into the ground by means of a pile-driving device above water, this can generate very high noise levels under water. As the noise is generated under water, the sound waves will be audible at a much greater distance from the sound source than if the sound source were above water. In practice, it has been found that when pile-driving activities are carried out, no other underwater activities can be carried out in the vicinity, that is to say within a radius of one kilometre or more, which require divers working under water. Sound sources other than a pile, for example a sonar or an explosive, such as a sea mine, or a cavitating screw of a vessel can also produce so much noise that this can result in damage to animals and humans in the vicinity of the sound source.
DE 10 2006 008095 A1 in the name of MENCK GMBH discloses a pile surrounded by a sleeve. The sleeve has a sandwich-type structure and comprises an inner wall and an outer wall. Sound-insulating material is provided between the inner wall and the outer wall and connects the inner wall and the outer wall to one another along the entire periphery, but under certain circumstances and in particular under water, this may cause undesirable transmission of sound vibrations.
JP 60 159218 A discloses a ramming hammer equipped with a sound insulator. Said sound insulator is a resilient bellows which can be arranged around a sound source. The sound insulator is filled with water. This sound insulator seems to be particularly suited for use on land and is not suitable to form and maintain an intermediate space under water.
DE 25 38 642 A1 does not relate to a sound insulator for a pile. The subject matter of this publication is a ramming hammer and in particular the operation thereof under water.
DE 22 37 133 A1 discloses a telescopic insulating screen. This insulating screen is unsuitable for underwater use since this involves large lateral forces which are due to for example tidal flows.
JP 05 030233 appears to disclose a sleeve, but this sleeve is not suitable to be used for maintaining a gas-filled space under water.
JP 04 070416 discloses a sound-insulating device for use on land which is unsuitable for use under water.